Solid state variable direction of view endoscope

ABSTRACT

An endoscope with a wide angle lens that comprises an optical axis that is angularly offset from a longitudinal axis of the endoscope such that the optical axis resides at an angle greater than zero degrees to the longitudinal axis. The wide angle lens system simultaneously gathers an endoscopic image field, the endoscopic image field at least spanning the longitudinal axis and an angle greater than ninety degrees to the longitudinal axis. The endoscope includes an optical lens system to at least partially even out the information density across an imaging surface area of the imager.

FIELD OF THE INVENTION

The present invention relates to variable direction of view endoscopes,in particular, variable direction of view endoscopes incorporating solidstate imagers and wide-angle lens systems. The present inventionincludes using a lens system to at least partially even out theinformation density across an imaging surface area.

BACKGROUND OF THE INVENTION

Variable direction of view endoscopes allow a user to change theendoscopic viewing direction without having to change the position ofthe endoscope itself. Such endoscopes are useful when a user wants tosee structures which are beside or behind the tip of the endoscope butcannot easily move the endoscope shaft because of anatomical constraintsor constraints imposed by other surgical instruments in the operativefield.

Variable direction endoscopy is desirable because it affords surgeonsgreater flexibility in their procedural approach. Increased viewingmobility improves the quality of diagnoses, as in cystoscopy forexample, where a typical diagnostic screening involves inspecting theinterior surface of the bladder for lesions or tumors. The ability tolook laterally and retrograde is important when doing this type ofdiagnosis because it makes it possible to visually cover the entirebladder surface, including the entrance region near the bladder neck. Inear-nose-throat and neurosurgical procedures, variable viewing isdesired because the procedures are delicate, and the entrance ports aresmall. It is therefore not possible to manipulate the endoscopesignificantly without injuring the patient. The ability to look sidewaysand backwards is important however during and after tumor resection whenit is necessary to keep track of tumor fragments, which if not caughtcan nucleate new tumors. Laparoscopy, another surgical discipline,imposes fewer maneuvering constraints but still benefits markedly fromvariable direction viewing because it allows surgeons to get betterobservation angles during a procedure and increases diagnosticcapabilities. Also, because of the greater viewing versatility, variabledirection of view endoscopes can minimize conflicts with other tools andcan simplify surgical planning by their ability to achieve standardviewing angles from nonstandard positions, allowing the surgeon to keepthe endoscope “off to the side” but still acquire the desired view.

A fundamental feature of variable direction endoscopy is that itgenerally makes it possible for surgeons to eliminate “blind movements.”A blind movement is the process of moving an instrument inside a patientwithout being able to see where the instrument is heading. This canoccur when it is necessary to advance a fixed-angle side viewingendoscope in its length direction without being able to see what isahead of the scope, or when a surgical tool has to be manipulated at theboundary of the endoscopic field of view.

Many known variable direction of view endoscopes also have drawbacks.First, these scopes use a movable image sensor or optical element at thetip of the scope to vary the viewing direction. Because of these movingparts, fabricating variable direction of view scopes is complicated andcostly, and such scopes are less robust than traditional fixed-anglescopes. Also, they often deliver inferior illumination and imagequality.

These scopes, both rigid and flexible tip endoscopes, also subject theuser to disorientation. As the endoscopic line of sight is changed, theuser faces two difficulties. The first is keeping track of where theendoscope is “looking.” With a rigid fixed-angle endoscope it isrelatively easy for the user to extrapolate the endoscopic viewingdirection from the position of the endoscope shaft. This is not the casewhen the viewing direction is regularly changed relative to thelongitudinal axis of the endoscope; the user quickly loses track ofspatial orientation within the anatomy being observed. The seconddifficulty is keeping track of what is “up” in the endoscopic image.Depending on the view-changing mechanism, the image will rotate relativeto the surroundings, and the user frequently loses visual orientation.This disorientation is often not correctable, especially in variabledirection of view scopes which have distal imagers and no facility forchanging image orientation.

Given the difficulties of variable direction endoscopes, it is commonfor surgeons to utilize rigid endoscopes with fixed viewing angles.Surgeons rely heavily on knowing that a certain endoscope provides a 30or 45 degree viewing angle. This preference for using multiple fixedangle endoscopes is due in part to the fact that a surgeon knows thatfor a particular endoscope they can dependably know what the anatomyshould look like. FIGS. 1A, 1B, 1C and 1D show the distal ends of fourcommercially available endoscopes 10, 20, 30, 40 with the most commonlyused viewing directions (view vectors) 50 corresponding to angularoffsets from the longitudinal endoscope axis 60 of 0, 30, 45, and 70degrees. Different surgical procedures typically require endoscopes ofmost of these angles with specific emphasis on one of them, often the 30degree endoscope because it provides both a good forward view and acertain amount of lateral viewing. However, in most procedures, such asear-nose-throat, bladder, orthopedic, brain, and abdominal procedures,lateral and partial retroviewing is beneficial and can be vital.Unfortunately surgeons often try to make due with only one or two scopesbecause changing the endoscope mid procedure is cumbersome (both lightand camera cables have to be disconnected and reconnected), timeconsuming, and sometimes dangerous. Also, inserting off-angle endoscopescan be dangerous because they are not “looking” in the direction theyare being inserted. This is a problem in neurosurgery, where surgeonsoften will not use 45- or 70-degree endoscopes because they are afraidof blindly thrusting the endoscope into delicate tissue.

Several designs have been proposed that provide solid state variabledirection of view endoscopes to reduce or eliminate the number of movingparts. U.S. Pat. Nos. 5,185,667 and 5,313,306 disclose using a fish-eyelens that provide a hemispherical field of view, i.e. the lens providesa wide angle image that provides variable viewing in both the x and ydirections. U.S. Pat. No. 6,449,103 discloses the use of an endoscopewith a catadioptric system. U.S. Pat. No. 5,800,341 discloses anendoscope with charged coupled devices (CCDs) forming a circumferentialband about the distal portion of the endoscope or CCDs coveringsubstantially all of the outer side wall of the shaft adjacent to thedistal end. U.S. Pat. No. 5,954,634 discloses the use of an image sensorat the proximal end of the endoscope that can move in a directionperpendicularly to the optical axis to enable selected portions of theimage field to be viewed. However, these solutions can be considereddeficient because they either provide poor resolution compared to astandard 70 degree field of view system, are overly complex and notfeasible to manufacture, do not provide retrograde viewing, i.e. viewingat an angle greater than 90 degrees relative to the axis of theendoscope in the distal direction, or still incorporate overly complexmechanics of design.

What is desired, therefore, is a variable direction of view endoscopethat can provide a feasible design and reduce the number of movingparts. It is further desired to provide an endoscope that can alsoprovide forward and retrograde viewing.

It is still further desired to provide an endoscopic system that enablesa surgeon to utilize reliable standard endoscopic viewing angles and atthe same time provide an overall field of view that encompasses theviewing range.

It is still further desired to provide a solid-state variable directionof view endoscope that has a resolution that is as high as theresolution of non-solid state variable direction of view endoscopes.

It is still further desired to provide a lens system in the solid-statevariable direction of view endoscope that evens out the informationdensity across an imaging surface area.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide anendoscope with an optical system that provides for f-sin(theta)distortion or f-theta distortion. In certain embodiments, the opticalsystem includes a wide-angle lens system that comprises an optical axisthat is angularly offset from a longitudinal axis of the endoscope suchthat the optical axis resides at an angle greater than zero degrees tothe longitudinal axis. In certain embodiments, the wide angle lenssystem simultaneously gathers light rays from an endoscopic image field,the endoscopic image field at least spanning the longitudinal axis andan angle greater than ninety degrees to the longitudinal axis. Incertain embodiments, the wide angle lens system includes a lens thatprovides for f-sin(theta) distortion or substantially f-sin(theta)distortion incorporated within the endoscope.

In certain embodiments, a lens system is used to at least partially evenout the information density across an imaging surface area. In certainembodiments, a wide-angle lens is used to at least partially even outthe information density across an imaging surface area. In certainembodiments, a lens system or a wide-angle lens is used to even out allof the information density across an imaging surface area.

In certain embodiments, a transmission system is not needed in order toeven out the information density across the imaging surface area. Incertain embodiments, additional subsystems are not needed in order toeven out the information density across the imaging surface area, as theobjective lens, which is a wide angle lens in certain embodiments, isused to even out all of the information density across an imagingsurface area.

In certain embodiments, the endoscope further comprises an imagercomprising an imaging surface area that receives at least a portion ofan endoscopic image transmitted by the wide angle lens system andproduces output signals corresponding to the endoscopic image field andimage forming circuitry that receives the output signal and produces animage signal. It is preferable that the imaging surface area isrectangular with the longitudinal dimension of the imaging surface areacorresponding to the longitudinal dimension of the endoscopic imagefield.

In certain embodiments, the imager only receives a portion of anendoscopic image transmitted by the wide angle lens system. In thisembodiment, the resolution of the image provided by the imager is ableto be increased so that it becomes as high as the resolution provided bya non-solid state variable direction of view endoscope.

In certain embodiments, the image transmission system distributes theangle of incidence of the light rays gathered from the endoscopic fieldof view onto the image surface area in order to even out the informationdensity across the imaging surface area. In certain embodiments, theimage transmission system distributes substantially all of the lightrays gathered from the wide angle lens system in the longitudinaldirection to correspond to the imaging surface area. In certainembodiments, the longitudinal direction of the imager spans the diameterof the captured endoscopic image field.

It is another object of the invention to provide an endoscopic systemwith image selecting circuitry that receives the image signal andproduces a region of interest signal that corresponds to a region ofinterest field that is less than the endoscopic image field. The regionof interest field can correspond to standard endoscopic viewing anglesof zero, thirty, forty-five, and seventy degrees. In certainembodiments, the endoscopic system can comprise image control circuitrythat receives a region of interest field selection from a user input andproduces a field control signal identifying the region of interestfield. The image selecting circuitry receives the field control signaland produces the region of interest signal in accordance with the fieldcontrol signal. The image selecting circuitry can rotate the imageformed by the region of interest signal about the axis of the viewingangle in order to alleviate disorientation by the user when switchingbetween standard endoscopic viewing angles.

In certain embodiments, the user input can enable a user to select atleast one preset standard endoscopic viewing angle and instructs theimage control circuitry to generate a field control signal in accordancewith that selection. In certain embodiments, the user input can furtherenable a user to select a progressive adjustment and produces anadjustment signal that incrementally alters the region of interest.

In certain embodiments, the endoscopic system can still further comprisevideo processing circuitry that generates video signals on the basis ofthe image signal and/or region of interest video signal and output allimage video signal or region of interest video signal respectively to adisplay. In certain embodiments, the video processing circuitry can alsoprovide a combined video signal comprising a first frame displaying theregion of interest video signal and a second frame displaying the allimage video signal.

It is yet another object of the present invention for the endoscope tocomprise a transmission system that distributes the angle of incidenceof the light rays gathered from the endoscopic field of view on to theimage surface area in order to at least partially even out theinformation density across the surface area. This can be provided by alens system that distributes substantially the entire endoscopic imagefield in the longitudinal direction to correspond to the imaging surfacearea. In certain embodiments, the distortion of this lens system is ofthe f-sin(theta) type. F-sin(theta) distortion means that the radialheight of an image at the sensor is proportional to the sine of thecorresponding object angle from which it originated.

A lens capable of f-sin(theta) distortion provides for a uniformf-number across the image plane. Therefore, image illumination and MTF(in the diffraction limit) will be uniform.

In certain embodiments, the imager receives only a portion of the lightrays gathered from the endoscopic field of view. This allows imagesreceived by the solid state variable direction of view endoscopes toapproach the resolution of a non-solid state variable direction of viewendoscope.

These and other objects of the invention are achieved by providing anendoscope, comprising: a lens system that comprises an optical axis thatis angularly offset from a longitudinal axis of the endoscope where theoptical axis resides at an angle greater than zero degrees to thelongitudinal axis; said lens system simultaneously gathering an imagefield spanning the longitudinal axis and an angle greater than ninetydegrees to the longitudinal axis; an imager having an imaging surfacearea, said imager receiving at least a portion of the image field andproducing an output signal related to the image field; imaging circuitrythat receives the output signal and produces an image signal; whereinsaid lens system at least partially redistributes the image field toeven out an information density across the imaging surface area.

In certain embodiments, said lens system includes a wide-angle lens,said wide angle lens at least partially redistributing the image fieldto even out an information density across the imaging surface area.

In certain embodiments, a lens system or a wide-angle lens is used toeven out all of the information density across an imaging surface area.

In certain embodiments, a transmission system is not needed in order toeven out the information density across the imaging surface area. Incertain embodiments, additional subsystems are not needed in order toeven out the information density across the imaging surface area, as theobjective lens, which is a wide angle lens in certain embodiments, isused to even out all of the information density across an imagingsurface area.

In certain embodiments, the endoscope further comprises image selectingcircuitry that receives the image signal and produces a region ofinterest signal that corresponds to a region of interest field that isless than the image field.

In certain embodiments, the endoscope further comprises an interfacethat enables a user to input an adjustment to the region of interest andproduces an adjustment signal that alters the region of interest.

In certain embodiments, said interface enables a user to rotate theimage formed by the region of interest signal.

In certain embodiments, said image selecting circuitry rotates the imageformed by the region of interest signal.

In certain embodiments, the rotation of the image is about the axis ofthe viewing angle.

In certain embodiments, the endoscope further comprises video processingcircuitry that generates a combined video signal comprising a firstframe displaying a region of interest video signal and a second framedisplaying an all image video signal.

In certain embodiments, the at least one lens distributes the imagefield in the longitudinal direction to correspond to the imaging surfacearea.

In certain embodiments, a longitudinal direction of the imager spans adiameter of the image field.

In certain embodiments, the imaging surface area is rectangular andcomprises a longitudinal dimension that is aligned with a longitudinaldimension of the image field.

In certain embodiments, the imaging surface area is square, circular oroval.

In certain embodiments, the imaging surface area has an HD aspect ratioof 16:9.

In certain embodiments, the endoscope further comprises an imagetransmission system.

In certain embodiments, said image transmission system at leastpartially redistributes the image field to even out an informationdensity across the imaging surface area.

Other objects of the invention are achieved by providing an endoscope,comprising: an optical system, the optical system including a wide anglelens system, the wide angle lens system having an optical axis that isangularly offset from a longitudinal axis of the endoscope such that theoptical axis resides at an angle greater than zero degrees to thelongitudinal axis, wherein the wide angle lens system simultaneouslygathers light rays from an endoscopic image field, the endoscopic imagefield at least spanning the longitudinal axis and an angle greater thanninety degrees to the longitudinal axis; an imager comprising an imagingsurface area that receives only a portion of an endoscopic imagetransmitted by the wide angle lens system and produces output signalscorresponding to the endoscopic image field; and image forming circuitrythat receives the output signal and produces an image signal, whereinsaid optical system at least partially redistributes the image field toeven out an information density across the imaging surface area.

In certain embodiments, the endoscope further comprises image controlcircuitry that receives a region of interest field selection from a userinput and produces a field control signal identifying the region ofinterest field; wherein the image selecting circuitry receives the fieldcontrol signal and produces the region of interest signal in accordancewith the field control signal.

In certain embodiments, the user input enables a user to select at leastone preset standard endoscopic viewing angle and instructs the imagecontrol circuitry to generate a field control signal in accordance withthat selection.

In certain embodiments, the endoscope further comprises an imagetransmission system.

In certain embodiments, said image transmission system at leastpartially redistributes the image field to even out an informationdensity across the imaging surface area.

Other objects of the invention are achieved by providing an endoscopecomprising: a shaft comprising a proximal end and a distal end and alongitudinal axis spanning the proximal end and the distal ends, thedistal end of the shaft being flexible; a handle coupled to the proximalend of the shaft; a wide-angle lens disposed in the distal end of theshaft, the wide angle lens gathering an endoscopic image field, saidwide-angle lens comprises having an optical axis that is angularlyoffset from a longitudinal axis of the endoscope such that the opticalaxis resides at an angle greater than zero degrees to the longitudinalaxis; and a solid state imager comprising an imaging surface area thatreceives at least a portion of endoscopic image transmitted by the wideangle lens system and produces output signals corresponding to theendoscopic image field, the solid state imager disposed in the distalend of the shaft, the wide-angle lens being disposed distally to thesolid state imager.

In certain embodiments, the endoscope further comprises image formingcircuitry that receives the output signal and produces an image signal;image selecting circuitry that receives the image signal and produces aregion of interest signal that corresponds to a region of interest fieldthat is less than the endoscopic image field; and image controlcircuitry that receives a region of interest field selection from a userinput and produces a field control signal identifying the region ofinterest field; wherein the image selecting circuitry receives the fieldcontrol signal and produces the region of interest signal in accordancewith the field control signal, wherein the region of interest fieldcorresponds to a standard endoscopic viewing angle.

In certain embodiments, the user input enables a user to select at leastone preset standard endoscopic viewing angle and instructs the imagecontrol circuitry to generate a field control signal in accordance withthat selection.

In certain embodiments, the user input enables a user to select aprogressive adjustment and produces an adjustment signal thatincrementally alters the region of interest.

In certain embodiments, the adjustment signal incrementally alters theviewing angle above or below the at least one preset standard endoscopicviewing angle.

In certain embodiments, the adjustment signal incrementally expands theregion of interest by incorporating pixels that longitudinally resideabove the original area of the region of interest and incorporatingthese pixels into the region of interest signal.

In certain embodiments, the endoscope further comprises an imagetransmission system, the image transmission system at least partiallyredistributing the image field to even out the information densityacross the imaging surface area.

In certain embodiments, the wide-angle lens simultaneously gathers anendoscopic image field at least spanning the longitudinal axis and anangle greater than ninety degrees to the longitudinal axis.

This application incorporates by reference in their entirety the subjectmatter of U.S. patent application Ser. No. 14/312,146 filed Jun. 23,2014; U.S. patent application Ser. No. 13/721,297, issued as U.S. Pat.No. 8,758,234; U.S. patent application Ser. No. 13/354,801, issued asU.S. Pat. No. 8,771,177; and U.S. patent application Ser. No.12/169,290, issued as U.S. Pat. No. 8,814,782.

Other objects of the invention and its particular features andadvantages will become more apparent from consideration of the followingdrawings and accompanying description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-D is a depiction of standard fixed angle endoscopic systems;

FIG. 2A is cross-section of the distal end of an embodiment of theendoscope of the present invention along the longitudinal axis;

FIG. 2B is a depiction of the image sensor of an embodiment of theendoscope of the present invention relative to the endoscopic field ofview;

FIG. 2C is a schematic of the circuitry for an embodiment of theendoscopic system of the present invention that provides for imageprocessing;

FIG. 3A is a depiction of information distribution upon an image sensorfrom a wide angle lens without image correction;

FIG. 3B is a depiction of information distribution upon an image sensorfrom a wide angle lens with image correction;

FIG. 4A is a depiction of a display generated by an embodiment of theendoscopic system of the present invention;

FIG. 4B is a depiction of another display generated by an embodiment ofthe endoscopic system of the present invention;

FIG. 5 is a cross-section of the distal end of the endoscope of thepresent invention along the longitudinal axis using a lens capable off-sin(theta) distortion;

FIG. 6 is a cross-section of the distal end of the endoscope of thepresent invention along the longitudinal axis using a lens capable off-sin(theta) distortion;

FIG. 7 is cross-section of the distal end of an embodiment of theendoscope of the present invention along the longitudinal axis; and

FIG. 8 is a graph of a normalized information density across the fieldof view at various locations in an image chain.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description illustrates the invention by way ofexample, not by way of limitation of the principles of the invention.This description will enable one skilled in the art to make and use theinvention, and describes several embodiments, adaptations, variations,alternatives and uses of the invention, including what is presentlybelieved to be the best mode of carrying out the invention.

FIG. 7 depicts a preferred embodiment of the present invention. FIG. 7depicts a distal tip 710 of an endoscope with a longitudinal axis 760, aviewing window 770, and a wide angle lens system 765 with opticalcenter. The optical center 761 is angularly offset from the longitudinalaxis 760 of the endoscope 710 and covers a viewing range 130 of 160degrees from −45 to +115 degrees relative to the longitudinal axis. Fromthis configuration, the wide angle lens system 765 simultaneouslygathers an endoscopic image field 730 that spans the longitudinal axisand an angle greater than ninety degrees to the longitudinal axis. As aresult, the simultaneous image field gathered by the endoscope providesboth forward and retrograde imaging. Providing a variable direction ofview endoscope that spans this range is beneficial because it enables auser to view objects that reside in front of the endoscope and behindthe standard fields of view for endoscopes. This improves the ability ofa user to safely operate and handle the device in the body cavity.Further by incorporating a wide angle lens with an optical center thatis angularly offset relative to the longitudinal axis, the endoscopewill be able to more accurately mimic the viewing capabilities andfunction of a fixed angle endoscope.

Additionally, FIG. 7 shows an endoscope without utilizing a transmissionsystem 150. Through testing, it was realized that an objective lensgroup, such as a wide angle lens, at least partially evens out theinformation density across an imaging surface area, and thus, in certainembodiments, a transmission system is not needed in order to even outthe information density across the imaging surface area.

FIG. 8 shows a chart of the normalized information density across fieldof view at various locations in the image chain. As shown, theinformation density is not uniform in at the object itself, but isuniform after the objective lens or the wide angle lens. Thisdemonstrates that the objective lens is doing substantial work in makingthe information density uniform.

In certain embodiments, the information density remains uniform goingthrough the other subsystems. In other words, they generate no change inthe information density, and all of the change in the informationdensity occurs via the objective lens.

In other embodiments, the objective lens at least partially evens outthe information density across an imaging surface area, and othersubsystems are responsible for additional changes in the informationdensity.

In certain embodiments, an image transmission system may be providedwithin the endoscope, such that the image transmission system at leastpartially evens out the information density across an imaging surfacearea and the objective lens also at least partially evens out theinformation density across an imaging surface area.

FIGS. 2A and 2B depict a preferred embodiment of the present invention.FIG. 2A depicts a distal tip 10 of an endoscope with a longitudinal axis60, a viewing window 70, a wide angle lens system 165 with opticalcenter 160 and a transmission system 150. The optical center 160 isangularly offset from the longitudinal axis 60 of the endoscope 10 andcovers a viewing range 130 of 160 degrees from −45 to +115 degreesrelative to the longitudinal axis. From this configuration, the wideangle lens system 165 simultaneously gathers an endoscopic image field130 that spans the longitudinal axis and an angle greater than ninetydegrees to the longitudinal axis. As a result, the simultaneous imagefield gathered by the endoscope provides both forward and retrogradeimaging. Providing a variable direction of view endoscope that spansthis range is beneficial because it enables a user to view objects thatreside in front of the endoscope and behind the standard fields of viewfor endoscopes. This improves the ability of a user to safely operateand handle the device in the body cavity. Further by incorporating awide angle lens with an optical center that is angularly offset relativeto the longitudinal axis, the endoscope will be able to more accuratelymimic the viewing capabilities and function of a fixed angle endoscope.As discussed in more detail below, while wide angle lenses arebeneficial in that they can increase the overall field of view, onedeficiency is that they tend to provide an uneven informationdistribution over the overall field of view, i.e. the resolution ofimages obtained at angles further away from the optical axis will bediminished. As a result, a wide angle lens with an optical center thatis angularly offset will enable the endoscope to produce higherresolution images at angles that correspond to standard fixed angleendoscopes. This will improve the willingness of surgeons to adopt anduse variable direction of view endoscopes.

Furthermore, having a wide angle lens with an optical center that isangularly offset has been shown to at least partially even out theinformation density across an imaging surface area. Through unexpectedtesting, it was realized that an objective lens (such as a wide anglelens) provided the majority of the evening out of the informationdensity across an imaging surface area.

The image field gathered by wide angle lens system 165 is conveyed totransmission system 150, which will be discussed in more detail below.Transmission system 150 in turn conveys the wide angle field of view toan image sensor that comprises image surface area 170. Image surfacearea 170 is formed by a plurality of pixels that gather and convertlight into output signals. Image surface area 170 is preferablyrectangularly shaped with a longitudinal dimension that is greater thanits lateral dimension, but can also be a variety of different shapes,such as square, circular or oval. Also, it is preferable that the imagesurface area 170 has an HD aspect ratio of 16:9. Since a wide-angle lenssystem can provide uneven information distribution, without correctionan HD image sensor enables the crowded information regions to becaptured and displayed on a monitor. As shown in FIG. 2B, image surfacearea 170 partially captures field 130. It is preferable that thelongitudinal dimension of image surface area 170 substantiallycorrespond to the entire longitudinal dimension of field 130. Thisenables the endoscopic system to provide the user with an image or arange of regions of interest that span the field of view of theendoscope. However, image surface area 170 only captures a portion ofthe lateral dimension of field 130. The lateral dimension of area 170can be chosen such that the distortion of an image laterally is minimaland not detected by the human eye. Further, by limiting the lateraldimension of the sensor, the cross-sectional area of the endoscope canbe more efficiently used. For instance, the lateral dimension of thewide angle lens can be reduced and consequently reduce the overall sizeof the endoscope. Also, the area of the field of view not captured bythe sensor can be used carry a fiber optic illumination system.

FIG. 2B also depicts specific regions of interest (ROIs) at 0, 30, 45and 70 degrees which can be selected by a user over a range 190 and isdiscussed in more detail below. A region of interest is an image areaformed on image surface area 170 that is a subset of the overall fieldof view captured by the sensor. The center of the area of the ROIcorresponds to a selected longitudinal viewing angle chosen by a user.The overall area of the ROI can correspond to the field of viewtypically provided by a fixed angled endoscope for that same angle.Alternative, the overall area of the ROI can be chosen to provide aminimal distortion variation across the overall area. This can beachieved by providing image selecting circuitry that forms a region ofinterest signal based on a predetermined set of sensor pixels.Alternatively, this can be achieved by providing an image selectingcircuitry that measures the degree of variance of an image signal forpixels that encompass the viewing angle and selects an area of the ROIbased on a distortion tolerance. Still further, the overall area of theROI can be chosen such that the field encompassed by a viewing angle atleast partially overlaps with an adjacent standard viewing angle, suchas 30 and 45 degrees. ROIs that are sized to overlap with adjacentviewing angles will assist a user in maintaining visual orientation inthe event that a viewing angle is changed.

As shown in FIG. 2C, image sensor 175 produces output signals 212 thatcorrespond to the endoscopic image field. Image forming circuitry 200receives the output signals and converts the signals into image signals214. Image signals 214 can be received by image selecting circuitry 202,which utilizes this signal to produce a region of interest signal 216.As discussed above, image selecting circuitry 202 forms ROI signal 216by selecting the portions of the image signal 214 that correspond to thepixels of sensor 170 that surround a particular viewing angle within agiven area. FIG. 2C also shows that the endoscopic system also comprisesa user input 206, from which a user can select a region of interestviewing angle. When a user selects a region of interest viewing angle,input 206 transmits a region of interest field selection 218 that isreceived by image control circuitry 204. Image control circuitry 204 inturn produces a field control signal 220 identifying the ROI. The fieldcontrol signal 220 is received by the image selecting circuitry 202,which generates a region of interest signal 216 in accordance with thefield control signal 220.

Preferably input 206 enables a user to select preset standard endoscopicviewing angles and instructs the image control circuitry to generate afield control signal in accordance with that selection. It is preferablethat the input 206 enables the user to select viewing anglescorresponding to 0, 30, 45 and 70 degrees relative to the longitudinalaxis of the endoscope.

It is also preferable that input 206 also provides a user with a nudge,or progressive adjustment, capabilities. In such an embodiment, input206 can provide a selection 218 that incrementally alters the ROI suchthat the user can see a portion of a cavity just outside the field ofview for the viewing angle. In one aspect, the input can provide aselection 218 that incrementally adjusts the viewing angle in thelongitudinal direction above or below the current viewing angle,shifting the pixels selected to form the ROI signal. Alternatively, theinput can provide a selection 218 that incrementally expands the area ofthe ROI in one longitudinal direction by incorporating additional pixelsthat reside in that direction in to the ROI signal. Another alternativeis to for the input to provide a selection 218 incrementally expands thearea of the ROI in both longitudinal directions by incorporating pixelsthat longitudinally reside outside the original area of the ROI andincorporating these pixels into the ROI signal. Giving a user theability to nudge enables the user to look slightly beyond what iscurrently shown in the ROI. Today surgeons using a fixed angle endoscopesometimes operate on the edge of the view field with limited visionbecause the endoscope cannot be manipulated to achieve the necessaryview. Slightly changing the orientation of a fixed angle endoscope orswapping one endoscope for another with a different viewing angle can becumbersome and dangerous. By incorporating a nudge feature, the user isable to start from a standard endoscopic viewing angle and slightlyshift the viewing angle to see what is outside the initial ROI. Also, ifa preset view angle does not provide the necessary field of view,changing to another preset viewing angle will require the surgeon tovisually reorient themselves. The nudge enables the surgeon to make aprogressive change to the viewing angle and helps avoid visualdisorientation.

Typically when a user switches between standard endoscopic viewingangles the user can become visually disoriented because the placement ofcommon anatomy within a body cavity at the second viewing angle willdiffer from objects visualized at the first viewing angle. To addressthis problem, it is preferable that input 206 enables a user to rotatean image formed within a ROI. In such an embodiment, input 206 canprovide a selection 218 to image control circuitry 204 to generate afield control signal 220 that instructs image selecting circuitry 202 torotate the image produced by the region of interest signal 216 about theviewing angle axis. This embodiment enables a user to electronicallycorrect the orientation of an endoscopic image in order to overcome anyproblems associated with visual disorientation.

The endoscopic system further includes video processing circuitry 208that converts the region of interest signal 216 and/or image signal 214into a video signal 222, which is received by a standard display 210.When the video processing circuitry 208 receives image signal 214, theprocessing circuitry generates an all image video signal. When the videoprocessing circuitry 208 receives ROI signal 214, the processingcircuitry generates a region of interest video signal.

FIG. 4A shows an embodiment of the image generated by video signal 222on display 210. Display 210 provides a video image 280 that includes afirst frame depicting the region of interest image 180 for a selectedviewing angle, in this case 45 degrees, and a second frame that displaysthe all image video signal 270. It is preferable that the all imagevideo signal 270 also include indicia 185 that show the location of theregion of interest image 180 relative to overall field of view. Videoimage 280 is beneficial because in most surgical situations it is usefulfor the surgeon to have the largest view of the entire field possible.However, as discussed below, very large fields of view can be subject tosignificant distortion and are not always optimal to use for surgicalvisualization. When a large field 270 is coupled with a local view 180associated with a ROI, it becomes useful because it helps the surgeonsee where the selected ROI 180 is located in the global surgicallandscape. FIG. 4B shows an alternative display scheme using a largemonitor 290 which displays a global image 270 and simultaneously a fullscale local image 180 on top of the global image.

In typical wide angle systems, the information density will vary acrossthe captured field, i.e. for viewing angles that are further away fromoptical center 160, such as the 0 and 70 degree viewing angles depictedin FIG. 2A, the information density can be substantially less thanoptical center. When such a wide angle field of view is projected on toa solid state imager, such as a CCD or CMOS imager, the resolution ofthe field at these viewing angles can be noticeably poor. As shown inFIG. 3A, the information density across image surface area 170 istypically greater towards the center of the imager and can decreasesubstantially across the imager in the longitudinal directions. Whilethe present invention can be implemented without adjusting for thisdifference in information density, it is preferable that endoscope 10provide a transmission system 150 that distributes the image field to atleast partially even out the information density across image surfacearea 170. To even out the information density and improve the resolutionof the imager as shown in FIG. 3B, it is preferable that transmissionsystem 150 is part of an f-theta optical system or an f-sin(theta)optical system.

An f-theta optical system uniformly separates the light rays incident towide angle lens 165 by a distance proportional to f-theta, where f isthe focal distance of the lens system and theta is the angle ofincidence of the image rays relative to optical axis 160. The f-thetaoptical system provides a uniform distribution of the image fieldrelative to the optical axis such that equivalent solid angles in theobject will be imaged onto equivalently sized regions of the imagingarea.

In an f-sin(theta) optical system the radial height of an image relativeto the image location of the optical axis is proportional to the sine ofthe corresponding object angle from which it originated. An f-sin(theta)optical system provides a uniform f-number across the image plane, andtherefore uniform illumination and potentially uniform MTF. Anf-sin(theta) optical system is an aspect of the optical system as awhole and is not separable from the wide angle aspect. In wide anglelens systems, the plano-concave front element of the objectivecontributes most (but not all) f-sin(theta) and wide angle aspects. Anf-sin(theta) optical system provides a larger field of view for theimage that is displayed.

FIG. 5 depicts another preferred embodiment of the present invention.FIG. 5 depicts a distal tip 510 of an endoscope with a longitudinal axis540, a viewing window 570, a wide angle lens system 565 with opticalcenter 560 and a transmission system 550. The optical center 560 isangularly offset from the longitudinal axis 540 of the endoscope 510 andcovers a viewing range 130 of 160 degrees from −45 to +115 degreesrelative to the longitudinal axis. From this configuration, the wideangle lens system 565 simultaneously gathers an endoscopic image field530 that spans the longitudinal axis and an angle greater than ninetydegrees to the longitudinal axis. As a result, the simultaneous imagefield gathered by the endoscope provides both forward and retrogradeimaging. Providing a variable direction of view endoscope that spansthis range is beneficial because it enables a user to view objects thatreside in front of the endoscope and behind the standard fields of viewfor endoscopes. This improves the ability of a user to safely operateand handle the device in the body cavity. Further by incorporating awide angle lens with an optical center that is angularly offset relativeto the longitudinal axis, the endoscope will be able to more accuratelymimic the viewing capabilities and function of a fixed angle endoscope.

The image field gathered by wide angle lens system 565 is conveyed totransmission system 550, which will be discussed in more detail below.Transmission system 550 in turn conveys the wide angle field of view toan image sensor.

Transmission system 550 includes a doublet lens 520 or an achromaticdoublet (double lens) 520. The doublet lens 550 is part of the lenssystem that is capable of providing f-sin(theta) distortion.

FIG. 6 depicts another preferred embodiment of the present invention.FIG. 6 depicts a distal tip 610 of an endoscope with a longitudinal axis640, a viewing window 670, wide angle lens system 665 with opticalcenter 660 and a transmission system 650. The optical center 660 isangularly offset from the longitudinal axis 640 of the endoscope 610 andcovers a viewing range 130 of 160 degrees from −45 to +115 degreesrelative to the longitudinal axis. From this configuration, the wideangle lens system 665 simultaneously gathers an endoscopic image field630 that spans the longitudinal axis and an angle greater than ninetydegrees to the longitudinal axis. As a result, the simultaneous imagefield gathered by the endoscope provides both forward and retrogradeimaging. Providing a variable direction of view endoscope that spansthis range is beneficial because it enables a user to view objects thatreside in front of the endoscope and behind the standard fields of viewfor endoscopes. This improves the ability of a user to safely operateand handle the device in the body cavity. Further by incorporating awide angle lens with an optical center that is angularly offset relativeto the longitudinal axis, the endoscope will be able to more accuratelymimic the viewing capabilities and function of a fixed angle endoscope.

The image field gathered by wide angle lens system 665 is conveyed totransmission system 650, which will be discussed in more detail below.Transmission system 650 in turn conveys the wide angle field of view toan image sensor.

Transmission system 650 includes a doublet lens 620 or an achromaticdoublet (double lens) 620. The doublet lens 620 is part of the lenssystem that is capable of providing f-sin(theta) distortion.

If the optical system does not correct the variation in informationdensity attributable to the wide angle lens system, then it may benecessary to provide circuitry that can correct any distortion or uneveninformation density that can be present in the image signal or theregion of interest signal. However, by utilizing an f-theta opticalsystem, the need to incorporate corrective circuitry and thecomplexities associated with such manipulation can be avoided.

The present invention merges the versatility of mechanical variabledirection of view systems with the relative simplicity of solid statedesigns. The advantage of the present invention is that it provides avariable direction of view system that reduces or eliminates the need touse complex mechanical systems. The present invention also overcomes anumber of disadvantages provided by typical wide angle endoscopicsystems that incorporate solid state imagers. The present invention canprovide a single instrument with no moving parts which provides thesurgeon with all the standard and familiar viewing directions andergonomics while maintaining excellent imaging performance.

The present invention has been described above in terms of a presentlypreferred embodiment so that an understanding of the present inventioncan be conveyed. However, there are alternative arrangements for a solidstate variable direction of view endoscope. The scope of the presentinvention should therefore not be limited by the embodiments discussed,but rather it should be understood that the present invention is widelyapplicable to variable viewing direction instruments in general. Allmodifications, variations, or equivalent elements and implementationsthat are within the scope of the claims should therefore be consideredwithin the scope of this invention.

What is claimed is:
 1. An endoscope, comprising: a lens system thatcomprises an optical axis that is angularly offset from a longitudinalaxis of the endoscope where the optical axis resides at an angle greaterthan zero degrees to the longitudinal axis; said lens systemsimultaneously gathering an image field spanning the longitudinal axisand an angle greater than ninety degrees to the longitudinal axis; animager having an imaging surface area, said imager receiving at least aportion of the image field and producing an output signal related to theimage field; imaging circuitry that receives the output signal andproduces an image signal; image selecting circuitry that receives theimage signal and produces a region of interest signal that correspondsto a region of interest field that is less than the image field; and aninterface that enables a user to input an adjustment to the region ofinterest and produces an adjustment signal that expands the region ofinterest by incorporating pixels that reside outside an original area ofthe region of interest into the region of interest signal; wherein saidlens system at least partially redistributes the image field to even outan information density across the imaging surface area.
 2. The endoscopeof claim 1, wherein said lens system includes a wide-angle lens, saidwide-angle lens at least partially redistributing the image field toeven out the information density across the imaging surface area.
 3. Theendoscope of claim 1, where said interface enables the user to rotatethe image formed by the region of interest signal.
 4. The endoscope ofclaim 1, where said image selecting circuitry rotates the image formedby the region of interest signal.
 5. The endoscope of claim 4, where therotation of the image is about the optical axis.
 6. The endoscope ofclaim 1, further comprising video processing circuitry that generates acombined video signal comprising a first frame displaying a region ofinterest video signal and a second frame displaying an all image videosignal.
 7. The endoscope of claim 1, where a longitudinal direction ofthe imager spans a diameter of the image field.
 8. The endoscope ofclaim 1, where the imaging surface area is rectangular and comprises alongitudinal dimension that is aligned with a longitudinal dimension ofthe image field.
 9. The endoscope of claim 1, where the imaging surfacearea is square, circular, or oval.
 10. The endoscope of claim 1, whereinthe imaging surface area has an HD aspect ratio of 16:9.
 11. Theendoscope of claim 1, further comprising an image transmission system.12. The endoscope of claim 11, wherein said image transmission system atleast partially redistributes the image field to even out theinformation density across the imaging surface area.
 13. An endoscope,comprising: an optical system, the optical system including a wide-anglelens system, the wide-angle lens system having an optical axis that isangularly offset from a longitudinal axis of the endoscope such that theoptical axis resides at an angle greater than zero degrees to thelongitudinal axis, wherein the wide-angle lens system simultaneouslygathers light rays from an endoscopic image field, the endoscopic imagefield at least spanning the longitudinal axis and an angle greater thanninety degrees to the longitudinal axis; an imager comprising an imagingsurface area that receives only a portion of an endoscopic imagetransmitted by the wide-angle lens system and produces output signalscorresponding to the endoscopic image field; image forming circuitrythat receives the output signal and produces an image signal; imageselecting circuitry that receives the image signal and produces a regionof interest signal that corresponds to a region of interest field thatis less than the image field; and an interface that enables a user toinput an adjustment to the region of interest and produces an adjustmentsignal that expands the region of interest by incorporating pixels thatreside outside an original area of the region of interest into theregion of interest signal; wherein said optical system at leastpartially redistributes the image field to even out an informationdensity across the imaging surface area.
 14. The endoscope of claim 13,further comprising image control circuitry that receives a region ofinterest field selection from the interface and produces a field controlsignal identifying the region of interest field; wherein the imageselecting circuitry receives the field control signal and produces theregion of interest signal in accordance with the field control signal.15. The endoscope of claim 14, wherein the interface enables the user toselect at least one preset standard endoscopic viewing angle andinstructs the image control circuitry to generate a field control signalin accordance with that selection.
 16. The endoscope of claim 13,further comprising an image transmission system.
 17. The endoscope ofclaim 16, wherein said image transmission system at least partiallyredistributes the image field to even out the information density acrossthe imaging surface area.
 18. An endoscope, comprising: a shaftcomprising a proximal end and a distal end and a longitudinal axisspanning the proximal end and the distal ends, the distal end of theshaft being flexible; a handle coupled to the proximal end of the shaft;a wide-angle lens disposed in the distal end of the shaft, thewide-angle lens gathering an endoscopic image field, said wide-anglelens comprises having an optical axis that is angularly offset from alongitudinal axis of the endoscope such that the optical axis resides atan angle greater than zero degrees to the longitudinal axis; a solidstate imager comprising an imaging surface area that receives at least aportion of an endoscopic image transmitted by the wide-angle lens andproduces output signals corresponding to the endoscopic image field, thesolid state imager disposed in the distal end of the shaft, thewide-angle lens being disposed distally to the solid state imager; imageselecting circuitry that receives the image signal and produces a regionof interest signal that corresponds to a region of interest field thatis less than the image field; and an interface that enables a user toinput an adjustment to the region of interest and produces an adjustmentsignal that expands the region of interest by incorporating pixels thatreside outside an original area of the region of interest into theregion of interest signal; wherein the wide-angle lens simultaneouslygathers the endoscopic image field at least spanning the longitudinalaxis and an angle greater than ninety degrees to the longitudinal axis.19. The endoscope of claim 18, further comprising: image formingcircuitry that receives the output signal and produces an image signal;image control circuitry that receives a region of interest fieldselection from the interface and produces a field control signalidentifying the region of interest field; wherein the image selectingcircuitry receives the field control signal and produces the region ofinterest signal in accordance with the field control signal; wherein theregion of interest field corresponds to a standard endoscopic viewingangle.
 20. The endoscope of claim 19, wherein the interface enables theuser to select at least one preset standard endoscopic viewing angle andinstructs the image control circuitry to generate the field controlsignal in accordance with that selection.
 21. The endoscope of claim 19,wherein the interface enables the user to select a progressiveadjustment and produces an adjustment signal that incrementally altersthe region of interest.
 22. The endoscope of claim 21, wherein theadjustment signal incrementally alters the viewing angle above or belowthe at least one preset standard endoscopic viewing angle.
 23. Theendoscope of claim 21, wherein the adjustment signal incrementallyexpands the region of interest by incorporating pixels thatlongitudinally reside above the original area of the region of interestand incorporating these pixels into the region of interest signal. 24.The endoscope of claim 18, further comprising an image transmissionsystem, the image transmission system at least partially redistributingthe image field to even out the information density across the imagingsurface area.
 25. The endoscope of claim 1, wherein the adjustmentsignal incrementally expands the region of interest by incorporatingpixels that reside outside the original area of the region of interestinto the region of interest signal.
 26. The endoscope of claim 1,wherein the adjustment signal expands the region of interest byincorporating pixels that longitudinally reside above the original areaof the region of interest into the region of interest signal.